Current sensing is required for a large array of applications, including load current control e.g. for chargers for portable devices. In such applications, it is important to have available a fast and accurate measurement of how much current is flowing into the load, e.g. for a reliable operation and control of a voltage supply. The requirement of high accuracy of the sense current conventionally makes it necessary to place a low offset, high gain amplifier inside the charge current control loop. However, such high gain, low offset amplifiers tend to be comparably slow. Moreover, conventional architectures tend to have the disadvantage of having poles below the unity gain frequency (UGF), wherein one or more of these poles may be charge current dependent. As a result, loop stability is difficult to achieve if a UGF above a given frequency shall be guaranteed.
Separating current measurement from current control would require provision of two dedicated sense paths and two low offset amplifiers, and therefore increase cost of the overall architecture. Using a fast, high gain and low offset amplifier might not be feasible in view of cost and/or circuit area.